Modern electric circuits or components have very complex internal functions, for example for digital/analog conversion, analog/digital conversion or for balancing of basic parameters of the components. Balancing of basic parameters can, for example, be performed via devices that are programmable one or several times, such as laser fuses, Zener zapping, cavity fuses or EEPROMs. However, sensor components in the magnetic range are mostly equipped with only a few pins. Reading out internal matter for test purposes or calibration or for writing with data is made much more difficult due to this bottleneck resulting from the few pins. Reading out internal matter should also be possible after housing the components. Thus, such processes are of importance, since some parameters can only be clearly defined and thus be programmed after a manufacturing process. This excludes the usage of laser fuses that can only be programmed on the chip.
Further, it has to be noted that the process of programming and reading out has sufficient interference immunity for industrial applications, has no unnecessary time losses due to speed or weighting times, and can no longer be activated later in the field, which would affect the basic function. However, the latter can be achieved by so-called “log bits”, which are set at the end of the calibration and programming process in the parameter memory of the device.
Normally, such components have three pins, wherein during application, two pins serve for supplying voltage potential and reference potential, and one pin as output pin for analog or digital data transfer.
U.S. Pat. No. 6,292,009 B1 describes a method for deriving a clock signal from a supply voltage signal. Thereby, merely the possibility is described to transmit data serially via a modulation method on an existing line with a static signal, namely the supply line. Thereby, terminals are saved. The need to transfer data in an interference-proof way is not mentioned, since this may not be required in the shown applications, namely in a relatively well-defined test environment.
DE 198 19 265 C1 describes also a possibility to transmit data via a supply voltage signal to a component. Thereby, however, the supply signal is raised to a range outside the normal operating range, which cannot occur in the application case. Thereby, the operation of the component is substantially limited to the configuration of the component. Exact performance analyses, for example by reading out analog/digital converter values, are only possible in a limited way due to the altered supply voltage conditions.
In the known methods, a component is placed into a configuration mode, where configuration data can be transferred to the component, by superimposing specific signals on the supply voltage. This is critical, since an inadvertent activation of such a configuration mode can occur by interferences on the supply voltage. In order to avoid such an inadvertent activation, the supply voltage potential can be risen to a range outside the normal operating range.
This is particularly critical for sensor circuits with an analog output, where the analog output signal depends on a supply voltage of the circuit. By increasing the supply voltage, the analog output signal would be corrupted.